Lighting Design Glossary

Aperture

(Term of photography)

The relative size of the lens opening in a camera,
expressed as an number (with prepended "f", eg: f8).
The counterpart to the aperture is the shutter speed,
expressed in fractions of a second.
If the numerical product of aperture and shutter
speed are the same, then the amount of light entering
the lens is the same. This amount is called the exposure.